Thermostatic heat conserving damper



Jan. 30, 1968 c. G. DIEHL THERMOSTATIC HEAT CONSERVING DAMPER Filed June 1, 1965 IAN 4 703.

FIGZ

United States Patent 3,366,333 THERMOSTATIC HEAT CGNSERVTNG DAMPER Charles G. Diehl, 6405 Osage Drive, North Little Rock, Ark. 72116 Filed June 1, 1965, Ser. No. 466,162 1 Claim. (Cl. 236-93) The subject invention relates generally to control means for exhaust fiues and the like and more particularly to a novel automatic vent control device for controlling the discharge of the products of combustion from space heaters, furnaces, hot water heaters and like devices while at the same time minimizing the loss of heat and conserving fuel consumed in such devices.

Many automatic flue control devices are in existence. For the most part, the known devices are designed to produce optimum draft conditions and to remain open at all times even when no combustion is taking place. By remaining open, particularly when no combustion is taking place, the known devices permit the heat in the combustion chamber as well as conditioned room air to es cape relatively rapidly due to normal convection conditions and otherwise. This loss of heat means that the furnace or like device must operate longer to generate the desired amount of useful heat and hence substantially increases the fuel consumption and cost of operation. The subject control device overcomes these and other shortcomings and disadvantages of existing devices by providing fine control means which open to an optimum condition only during actual combustion periods to allow for the escape of the products of combustion but otherwise remain substantially closed to prevent undesirable loss of hot and cold air including furnace as well as room conditioned air. The subject control is preferably constructed to allow some predetermined leakage sufficient to maintain a pilot light and for other safety purposes and is also constructed to have substantially uniform opening and closing characteristics proportional to the stack temperature over its full operating range. Furthermore, the subject device may have built into it fail safe features.

It is therefore a principal object of the present invention to reduce the operating cost of furnaces and other combustion type heating devices.

Another principal object is to minimize the loss of conditioned hot and cold air through an exhaust outlet.

Another object is to minimize waste and reduce the fuel consumption of furnaces, space heaters, hot water heaters and like devices.

Another object is to minimize pilot light failures caused by drafts and to enable pilot lights to be operated with less fuel consumption.

Another object is to provide automatic flue control means which remain substantially closed to prevent undesirable loss of heat during periods when no combustion is taking place.

Another object is to provide a relatively inexpensive automatic flue control device which can be installed in new as well as in existing furnace fines and the like by relatively unskilled personnel.

Another object is to provide an automatic flue control device with built in fail safe features.

Another object is to provide an automatic flue control having operating characteristics which are proportional to the stack temperature.

Another object is to provide flue control means which can be preassembled in a convenient form for ease in handling, packaging and installing.

These and other objects and advantages of the present invention will become apparent after considering the following detailed specification covering a preferred embodiment in conjunction with the accompanying drawing, wherein:

FIG. 1 is a top view of an automatic flue control device constructed according to the present invention; and

FIG. 2 is a cross-sectional view taken on line 22 of FIG. 1 showing the device in closed condition in solid outline and in an open condition in dotted lie.

Referring to the drawing more particularly by reference numbers, the number 8 in FIG. 1 refers to a control device constructed according to the present invention. The device 8 includes an annular ring or frame member If? mounted by suitable means, such as rivets 12, inside a section of flue pipe 14. The pipe section 14 may be a sheet metal pipe section of a standard size and known construction such as are commonly used for the exhaust fines of furnaces, hot water heaters, space heaters and other like devices. The pipe section 14 can also be modified or strengthened by corrugations such as the corrugations 15.

A shaft 16 is mounted extending across the frame 10 and the pipe 14 and is maintained in a fixed position in the frame 10 by pins 18 which extend into aligned holes in the frame 19 and in the shaft 16. One end of each of the pins 18 also extends outwardly from the frame 10, as shown, to form stops for engaging a movable damper plate 20. The free end of at least one of the pins 18 may be bent or formed to stop the damper plate 20 at any desired fully open position. The damper plate 20 is stopped in its closed position by engagement with the frame 10 as will be shown.

The damper plate 20 is substantially round in shape and is provided across a diameter thereof with alternate oppositely formed rounded portions 22 and 24. The rounded portions 22 and 24 together define a passage which receives the shaft 16. The connection between the plate 20 and the shaft 16 should be relatively free to allow the damper plate 2% to move between its open and closed positions.

The inner turn of a helical shaped bi-metal element 26 is mounted on the shaft 16 as shown in FIG. 2 and is anchored to the shaft by cooperation between an integral right angle tab 28 formed on the inner end of the helical element and a groove 39 formed in the shaft 16. The groove 3! preferably extends at least to one end of the shaft 16 to facilitate assembly of the helical element thereon when the shaft 16 is moved therethrough. The bimetal element 26 is constructed to expand and contract in response to changes in temperature.

The bi-metal element 26 is located in an oversized opening 32 in the damper plate 20, and the outer end of the element 26 is provided with an integral outwardly extending end portion 34 which is positioned extending through a passage in the plate 20 formed by a knockout 36. It is preferred that the sliding connection between the element portion 34 and the plate 20 be as free sliding as possible so that the different operating positions of the plate 29 will be substantially in proportion to temperature. This means that the heat reaching the flue during combustion will relatively accurately control the position of the damper plate Zll to produce optimum draft conditions. This is particularly desirable in larger size lines where precise hue control becomes even more important.

The diameter of the damper plate 29 is also preferably smaller than the inside diameter of the flue pipe 14 so that it will freely operate in all positions and yet in the closed position will engage the frame llll around substantially its full circumference to provide a relatively leakproof connection therebetween. This is possible because the frame 1! is constructed of two integral ofiset semi-circular portions Ilia and 1011 with surfaces 38 and 4%) respectively (FIG. 2) which are engaged by the damper 2% in the closed position thereof. This means that in the closed position substantially the only leakage will be through the Opening 32, and this leakage can be relatively accurately controlled by proper construction of the opening 32 and proper sizing of the bi-metal element 26. The construction and the manner in which the frame it) is installed in the pipe section 14 also provides a relatively rugged assembly which is able to withstand unusually rough handling without damage.

When the subject device is installed in a line the hot 'gases which are produced during combustion will rise in the flue through and past the damper plate 20. At the beginning of a combustion period the hot gases will only be able to pass through the small opening 32 past the bi-rnetal element 25. This will cause the bimetal element 26 to expand and in so doing will move the damper plate 20 from its closed position to an open position out of engagement with the frame 10. As the damper Opens the products of combustion can escape other than through the opening 32, thereby causing a somewhat less concentration of heat around the oi-metal element 26 and this may cause the damper to partially reclose to a final optimum draft condition. As the furnace temperature continues to rise the flue temperature will also rise causing the damper to become more open during a combustion period. This is desirable because it provides automatic optimum flue control which promotes efiicient operation and utilization of the fuel. Thereafter at the conclusion of a combustion period the element 26 will be subjected only to the residual heat remaining in the furnace which is usually at a somewhat lower temperature than during combustion. Under this reduced temperature condition the element 26 will react to move the damper plate 20 to its closed condition to prevent the escape of heat from the furnace. The closing of the damper preferably takes place relatively rapidly after the end of a combustion period to prevent escape of most of the residual heat in the furnace. By so doing a substantial amount of the residual heat will be trapped for use and a substantial reduction in fuel will be made. The efficiency of the furnace will therefore be substantially increased by the present device. Under actual test conditions very substantial fuel savings have been achieved. This has not been true of any known flue control devices, however, all of which are designed to remain substantially open at all times but are regulated to produce optimum draft conditions during combustion periods. In other words, the known devices move toward a controlled partially closed condition only during combustion periods but otherwise remain open, not closed.

The damper plate 20 in the present device may be weighted on one side of the shaft 16 by means such as weight member 42 to cause it to automatically move to an open position in the event the element 26 breaks or relaxes its tension. This is a safety feature which may be built into the device.

With the subject device the operating condition of the bi-metal strip 26 can be accurately calibrated in advance to cover the full range of expected temperatures depending on the type of unit on which it is installed and the temperatures expected. It should also be pointed out that when a combustion cycle begins the products of combustion are initially concentrated in the opening 32 and around the bi-metal element 26. This may accelerate the initial opening of the damper which is a desirable condition. Thereafter, the damper may overshoot its'final open position for the temperature and then settle back to the optimum draft condition as explained above.

Inasmuch as the subject control is closed when the furnace or other heating device is not in a combustion cycle it also acts to minimize escape of furnace or heater air as well as conditioned air in the surrounding room. This may include both warm room air in the winter time and cool air conditioned air in the summer time. lso by being normally closed when the furnace or other device is not operating down-drafts caused by gustiness or otherwise as well as up-drafts caused by convection and vacuum uplift are prevented. In the winter this results in a considera'ole saving in fuel and in the summer reduces the cost of operating air conditioning equipment and particularly central air conditioning equipment. Closing the flue also prevents down-draft from'blowing out the pilot and results to some extent to conserving the heat generated by the pilot light. This also may enable the pilot light to be operated less intensely thereby resulting in a further saving in fuel.

Thus there has been shown and described a novel control device which fulfills all of the objects and advantages sought therefor. Many changes, modifications, variations and other uses and applications of the present device will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawing. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claim which follows.

What is claimed is:

1. Means for controlling the discharge of the products of combustion from an exhaust fiue of a heating device such as a furnace or the like comprising an open ended tubular flue section adapted to be installed as part of an exhaust flue, a frame member mounted to the inside of the flue section, a shaft member mounted on said frame in position extending across the inside of the flue section, a damper plate hingedly mounted on said shaft and movable thereon between a closed position extending across the flue section and engaged around the periphery thereof with the frame member to substantially restrict communication therethrough and an open position angularly related to the closed position to provide communication through the flue section, and an elongated bi-metal element wound in helical form, said elongated helical shaped element having a smaller diameter inner end portion just large enough to receive the shaft on which the damper plate is mounted, and a larger diameter outer end portion,

the inner end portion of said element having an inwardly extending tab formed on the end thereof which tab cooperates with a groove formed in the shaft to prevent relative movement therebetween, the larger diameter outer end portion of said binetal element having an outwardly extending tab portion thereon, means including said outwardly extending tab portion forming a sliding connection between the bi-metal element and the damper plate to relieve radial stresses in the bi-metal element during operation thereof, said sliding connection including means on the damper plate for slidably receiving the outwardly extending tab portion, said bi-metal element operating to move said damper platetoward a more open position in response to increases in the due temperature.

References Cited EDWARD 1. MICHAEL, Primary Examiner. 

1. MEANS FOR CONTROLLING THE DISCHARGE OF THE PRODUCTS OF COMBUSTION FROM AN EXHAUST FLUE OF A HEATING DEVICE SUCH AS A FURNACE OR THE LIKE COMPRISING AN OPEN ENDED TUBULAR FLUE SECTION ADAPTED TO BE INSTALLED AS PART OF AN EXHAUST FLUE, A FRAME MEMBER MOUNTED TO THE INSIDE OF THE FLUE SECTION, A SHAFT MEMBER MOUNTED ON SAID FRAME IN POSITION EXTENDING ACROSS THE INSIDE OF THE FLUE SECTION, A DAMPER PLATE HINGEDLY MOUNTED ON SAID SHAFT AND MOVABLE THEREON BETWEEN A CLOSED POSITION EXTENDING ACROSS THE FLUE SECTION AND ENGAGED AROUND THE PERIPHERY THEREOF WITH THE FRAME MEMBER TO SUBSTANTIALLY RESTRICT COMMUNICATION THERETHROUGH AND AN OPEN POSITION ANGULARLY RELATED TO THE CLOSED POSITION TO PROVIDE COMMUNICATION THROUGH THE FLUE SECTION, AND AN ELONGATED BI-METAL ELEMENT WOUND IN HELICAL FORM, SAID ELONGATED HELICAL SHAPED ELEMENT HAVING A SMALLER DIAMETER INNER END PORTION JUST LARGE ENOUGH TO RECEIVE THE SHAFT ON WHICH THE DAMPER PLATE IS MOUNTED, AND A LARGER DIAMETER OUTER END PORTION, THE INNER END PORTION OF SAID ELEMENT HAVING A INWARDLY EXTENDING TAB FORMED ON THE END THEREOF WHICH TAB COOPERATES WITH A GROOVE FORMED IN THE SHAFT TO PREVENT RELATIVE MOVEMENT THEREBETWEEN, THE LARGER DIAMETER OUTER 